A fuse unit is proposed in which a conductive circuit body that has a bus bar with which a fuse element (fusible body) is integrally formed is molded integrally with an insulating resin housing, and the circuit body and the fusible body are embedded in the resin housing. Since, in this fuse unit, the fusible body is formed integrally with the circuit body, labor of connecting the fusible body to the circuit body is saved and assemblability is improved.
However, in the fuse unit in which the circuit body and the fusible body are integrally formed, when an electric current of a specified value or more (an overcurrent) flows and the fusible body fuses, it cannot be replaced with a substitute fusible body and the whole fuse unit should be replaced.
In addition, in a case where the circuit body and the fusible body are integrally formed, since it results in a fuse capacity of the same plate thickness as the plate thickness of the circuit body, that is, the same sectional area, the plate thickness cannot be thickened, that is, the sectional area cannot be largely taken in order to energize a fusible body for large current. Therefore, in the fuse unit having the circuit body which is integrally formed with the fusible body, a resistance value that is commensurate with a required fuse capacity cannot be set.
Accordingly, a fuse unit configured such that the fusible body is provided separately from the circuit body, and the fusible body for which the resistance value that is commensurate with the required fuse capacity is set is incorporated into the circuit body is proposed in Patent Literature 1. In this fuse unit, the separately provided fusible body is joined with the circuit body by various joining methods such as welding with solder, swaging, welding with ultrasonic waves, and welding with optical laser beams. In addition, in the fuse unit in this Patent Literature 1, an example is also proposed in which in a case where the fusible body has fused, the substitute fusible body can be fixed to a fixing part that is provided in advance on the fusible body.